The human skeleton consists of plural kinds of so many bones such as upper and lower jawbones, spine or skull, and for example a case to drill the upper and lower jawbones for implant or a case to drill spine or skull for surgery related diseases is frequently occurred.
Many tools such as drills to drill various bones are developed, and a representative example is disclosed in ┌ENDOSSEOUS IMPLANT DRILL┘ of U.S. Pat. No. 6,641,395. The representative components are shown in FIGS. 1 and 2.
FIG. 1 is a side view of a conventional implant drill bit, and FIG. 2 is an enlarged view of FIG. 1.
As shown in FIG. 1, an implant drill bit 10 consists of a mounting portion 22 to be mounted a dental hand-piece, a working portion 24 for cutting bones and a collar 26 to connect them.
The working portion 24 includes a plurality of “V” typed longitudinal channels 39. The plurality of “V” typed longitudinal channels 39 defines a plurality of end cutting blades 36 and a plurality of axial cutting edges 34 which are finished at a cutting tip 35 inclusive of a distal-most end 38. The plurality of axial blades 34 is straightly extended almost parallel to a longitudinal axis 11, and they are arranged with equal interval in about 120°. And, the working portion 24 includes a longitudinal fluid passageway 40 from which a fluid is passed through a collar through hole 32.
Each blade 34 has a leading blade surface 34a, a trailing blade surface 34b, a leading side edge 37a and a trailing side edge 37b. On the trailing blade surface 34b of the blades 34, fluid discharge ports 42 are formed adjacent to the end cutting blades 36.
Each end cutting blade 36 has a leading cutting edge 36a and a trailing edge 36b to form a relief surface 122 there-between, a leading blade surface 124 and a trailing blade surface 120, and also the crossing portion of the leading blade surface 124 and the relief surface 122 will be the leading edge 36a. Furthermore, each end cutting blade 36 includes a leading edge 46a and a trailing edge 46b, or connects to them. The leading blade surfaces 124 have inner edges 72 oriented at an angle θ with respect to the longitudinal axis 11, and the end cutting blades 36 are diverged at an angle β(<90°) with respect to the longitudinal axis 11.
The conventional implant drill bit 10 having the above-explained structure, leading blade surfaces 124 have inner edges 72 oriented at an angle θ with respect to the longitudinal axis 11, and the end cutting blades 36 are diverged at an angle β(<90°) with respect to the longitudinal axis 11, and therefore it can cut a desired amount of bones in short time and then can easily drill holes in a desired depth.
However, the conventional drill bit 10 can be moderately applied to cases in that bone depth is enough deep, bone thickness is enough thick, or fortunately other important parts such as membranes, nerves or cells are not present, but in cases that bone depth is light, bone thickness is thin, or fortunately other important parts such as membranes, nerves or cells are present, even a very skillful person should very carefully do drilling to give no damage to these important parts. Furthermore, in case that the drilling is proceeding in high speed of 2,000˜10,000 rpm, by even very skillful person, unwanted problems are often occurred, for example, other important parts such as membranes, nerves or cells are damaged or the membranes are torn, the nerves or cells are died.